1. Field of the Invention
The present invention relates to a drive device for a vehicle, which is installed on the vehicle and transmits motive powers from an internal combustion engine and an electric motor to driven parts while changing speeds of the motive powers.
2. Description of the Related Art
Conventionally, as a drive device for a vehicle, one disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2008-302800 is known. This drive device for a vehicle is applied to a four-wheel vehicle, and transmits motive powers of the engine and the electric motor to drive wheels while changing the speeds of the motive powers. The drive device includes an input shaft connected to the engine, an output shaft connected to the drive wheels, two counter shafts connected to the input shaft via two clutches, and so forth. A gear group forming a first-speed to sixth-speed forward positions, a synchronization mechanism for connecting and disconnecting the first-speed to sixth-speed forward positions, and an actuator for actuating the synchronization mechanism are arranged between the two counter shafts and the output shaft. Further, the electric motor is connected to a transmission gear for the first-speed forward position. Note that throughout the specification, the synchronization mechanism and the actuator for actuating the synchronization mechanism are collectively referred to as the “synchronizer”.
In the drive device for a vehicle, at the standing start of the vehicle, first, the first-speed forward position is switched to an in-gear state by the synchronizer. When the charge level of a battery is high enough, electric power of the battery is supplied to the electric motor, whereby the motive power of the electric motor is transmitted to the drive wheels via the first-speed forward position. On the other hand, when the charge level of the battery is not high enough, the motive power of the engine is transmitted to the drive wheels via the first-speed forward position.
According to the above-described conventional drive device for a vehicle, the electric motor is connected to the transmission gear for the first-speed forward position, and hence when the first-speed forward position is switched to the in-gear state at the standing start of the vehicle, there is a fear that an in-gear operation for switching the first-speed forward position to the in-gear state using the synchronizer fails, because the rotor of the electric motor acts as an inertial resistance. Although this problem can be solved by increasing the volume of the synchronization mechanism of the synchronizer or increasing the size of the actuator of the synchronizer, in a case where the synchronizer is configured as such, this is accompanied by an increase in the weight and size of the synchronizer, and accordingly such configuration brings about an increase in the manufacturing costs thereof and a lowered degree of freedom in design.